Sensor systems

ABSTRACT

A sensor assembly includes a frame defining a sensor axis having opposing endplates with axially extending supports. The opposing endplates are connected by a pair of axially extending side beams. A suspended mass is within an interior of the frame suspended from the supports of the frame. A plurality of piezoelectric material layers are operatively connected to sides of respective spacers opposite the frame to damp vibrations of the suspended mass.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/612,170 filed Feb. 2, 2015, which is incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to sensor systems, and more particularlyto sensor assemblies such as those used in imaging devices.

2. Description of Related Art

A variety of devices and methods are known in the art for sensor systemson aircraft. One parameter that directly affects the quality of many ofthe images collected by the sensor systems is line-of-sight (LOS)stabilization. One source of sensor LOS destabilization is vibrationwithin the sensor system. Vibrations can be created by environmentalinfluences on the sensor system (e.g. wind drag and turbulence), byoperational factors, by platform sources (e.g. aircraft vibrations) andby components within the sensor itself (e.g. fans, heaters, etc.). Byreducing or damping vibrations acting on the sensor system, LOSstabilization can be improved, resulting in improved quality of imagesand other data captured by the sensor.

Current sensor systems have generally been considered satisfactory fortheir intended purpose. However, there is still a need in the art forimproved sensor systems. The present disclosure provides a solution forthis need.

SUMMARY OF THE INVENTION

A sensor assembly includes a frame and a suspended mass within aninterior of the frame defining a sensor axis. The sensor assemblyincludes a piezoelectric material layer operatively connected to theframe to damp vibrations of the suspended mass.

The frame can include composite layers, for example, fiber reinforcedpolymer (FRP) composite layers. The piezoelectric material layer can belayered between the FRP composite layers. The piezoelectric materiallayer can be a macro-fiber composite (MFC) piezoelectric material layer.The frame can include inwardly extending supports to which the suspendedmass is suspended from. At least one of the inwardly extending supportscan include FRP composite layers. The piezoelectric material layer canbe operatively connected to one of the supports of the frame. Thepiezoelectric material layer can be layered within the FRP compositelayers of at least one of the supports of the frame. The frame caninclude a pair of endplates spaced apart from one another along thesensor axis, and a pair of axially extending side beams connecting thepair of endplates. At least one of the endplates can include FRPcomposite layers. The piezoelectric material layer can be operativelyconnected to an outer surface of one of the endplates of the frame. Thepiezoelectric material layer can be operatively connected to an innersurface of one of the endplates of the frame. It is contemplated thatthe piezoelectric material layer can be layered within the FRP compositelayers of at least one of the endplates of the frame.

In accordance with another aspect, a sensor assembly includes a framedefining a sensor axis having opposing endplates with axially extendingsupports. The opposing endplates are connected by a pair of axiallyextending side beams. A suspended mass is suspended within an interiorof the frame from the supports of the frame. A plurality ofpiezoelectric material layers are operatively connected to the endplatesand supports of the frame to damp vibrations of the suspended mass.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 is a perspective view of an exemplary embodiment of a sensorsystem constructed in accordance with the present disclosure, showingthe frame and the suspended mass;

FIG. 2 is a top plan view of the sensor system of FIG. 1, showing thesupports;

FIG. 3 is a perspective view of another exemplary embodiment of a sensorsystem constructed in accordance with the present disclosure, showingthe frame and the suspended mass;

FIG. 4 is a top plan view of the sensor system of FIG. 3, showing thesupports and the endplates having a piezoelectric material layer;

FIG. 5 is a side elevation view of a portion of the sensor system ofFIG. 3, showing the surface of the spacer at an angle with respect to asurface of the frame;

FIG. 6 is a cross-sectional end view of the sensor system of FIG. 3,showing the supports with a spacer between a side of the stub beam andthe piezoelectric material layer;

FIG. 7 is a perspective view of another exemplary embodiment of a sensorsystem constructed in accordance with the present disclosure, showingthe frame and the suspended mass and a piezoelectric material layer onthe frame;

FIG. 8 is a top plan view of the sensor system of FIG. 7, showing thesupports having piezoelectric material layers;

FIG. 9 is a perspective view of another exemplary embodiment of a sensorsystem constructed in accordance with the present disclosure, showingthe frame and the suspended mass, with a piezoelectric material layerlayered within an endplate of the frame;

FIG. 10 is a top plan view of the sensor system of FIG. 9, showingpiezoelectric material layers layered within the supports; and

FIG. 11 is a cross-sectional end view of the sensor system of FIG. 9,showing composite layers of the frame with the piezoelectric materiallayer therebetween.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of a sensorassembly constructed in accordance with the disclosure is shown in FIG.1 and is designated generally by reference character 100. Otherembodiments of sensor assemblies in accordance with this disclosure, oraspects thereof, are provided in FIGS. 2-11, as will be described. Thesystems and methods described herein can be used to reduce vibrationexperienced by sensor assemblies and reduce the weight of sensorassemblies.

As shown in FIG. 1, a sensor assembly 100 includes a frame 102, asuspended mass 104 within an interior of frame 102 defining a sensoraxis A, and a spacer 106 operatively connected to frame 102. Apiezoelectric material layer 114 is operatively connected to a side ofspacer 106 opposite of frame 102 to damp vibrations. Those skilled inthe art will readily appreciate that suspended mass 104 can include avariety of electrical, optical and/or mechanical sensor components,and/or accessories therefor. It is contemplated that piezoelectricmaterial layer 114 can be a macro-fiber composite (MFC) piezoelectricmaterial layer, such as an MFC piezoelectric material available fromSmart Material Corp., Sarasota, Fla. A MFC piezoelectric materialincludes piezoelectric ceramic fibers arranged in a specific sequencethat results in an electro-mechanical response either when exposed tostrains created by vibration-induced material deformation or whencommanded to exert mechanical force that creates material deformation byapplying a specifically controlled electrical signal to the MFC. Thiselectro-mechanical response can be commanded to elongate or contract thestructure to counteract unwanted measured vibrational strains, providinga lightweight alternative to traditional damping systems.

With continued reference to FIG. 1, spacer 106 acts as a moment arm toincrease the damping effect of piezoelectric material layers 114. Thoseskilled in the art will readily appreciate that spacer 106 can be anon-piezoelectric material spacer and/or can be a MFC piezoelectricmaterial spacer. It is contemplated that if spacer 106 is apiezoelectric material electrically connected in a similar manner aspiezoelectric material layer 114, the overall damping force applied at agiven location can be doubled. Even if not electrically charged, aspacer 106 that is a piezoelectric material would act to increase themoment arm but would not impart any damping force itself. Those skilledin the art will readily appreciate that one or more spacers 106 can beused, and/or piezoelectric material layer 114 can be laminated onto asurface of spacer 106. Additionally, it is contemplated that the shapeand thickness of spacer 106 can vary as needed for a given application.

In use, piezoelectric material layer 114 can be actively or proactivelycontrolled. For example, for active control in accordance with someembodiments, piezoelectric material layers 114 are operatively connectedto a digital signal processor. The digital signal processor can provideinstructions to piezoelectric material layers 114 based on real-timevibration data received from vibration sensors arranged throughoutsensor assembly 100 to actively damp vibrations in assembly 100 via aclosed-loop arrangement. For proactive control, an electric signal canbe used to actuate piezoelectric material layers 114 based uponcharacteristic information of vibration causing influences measuredprior to the real-time events that cause the vibration, such asturbulence, to proactively damp vibrations in the frame.

Now with reference to FIG. 2, frame 102 includes inwardly extendingsupports 108 to which suspended mass 104 is suspended from, and a pairof endplates 110 spaced apart from one another along sensor axis A. Apair of axially extending side beams 112 connect endplates 110. Spacers106 and piezoelectric material layers 114 are arranged in a mirroredconfiguration with respect to an axis T transverse to longitudinal axisA. This mirrored configuration permits piezoelectric material layers 114to apply equal and opposite damping forces, therein providing evendamping to the frame.

As shown in FIG. 3, a sensor assembly 200, similar to sensor assembly100, includes a frame 202, a suspended mass 204 defining a sensor axisA, and a spacer 206 operatively connected to frame 202. A piezoelectricmaterial layer 214 is operatively connected to a side of spacer 206opposite of frame 202 to damp vibrations. Spacers 206 on endplate 210 ofsensor assembly 200 are wedged shaped. Each wedged shaped spacer 206permits its respective piezoelectric material layer 214 to apply forcein two directions. For example, piezoelectric material layers 214 onendplates 210 apply force in a z direction and a y direction, whilepiezoelectric material layers 214 on supports 208 apply force in an xdirection and a y direction. It is contemplated that the wedge shape canbe altered to provide damping forces in the desired directions.

With reference now to FIGS. 4-6, spacers 206 are operatively connectedto endplates 210 and supports 208 of frame 202. While spacers 206 andtheir corresponding piezoelectric material layers 214 are describedherein as being placed on supports 208 and endplates 210 of frame 202,it is contemplated that spacers 206 and piezoelectric material layers214 can be can be placed in a variety of locations on frame 202 thatexperience or are expected to experience vibration induced displacementor deflection. For example, a 3-dimensional arrangement of piezoelectricdevices, as shown in FIGS. 3-6, would be required to cancel3-dimensional vibrational influences. Wedged shaped spacers 206 includea spacer surface 216 at an angle with respect to which ever framesurface to which it is operatively connected. For example, spacersurface 216 is at an angle with respect to endplate outer surface 218.This is shown by an axis X extending perpendicularly from surface 216being at an angle with respect to longitudinal axis A, which isperpendicular to endplate outer surface 218. Spacer surface 216 is alsoat an angle with respect to a surface 220 of one of supports 208. Theangle of spacer surface 216 with respect to whichever frame surface itis operatively connected to ranges from 1 degree to 45 degrees, forexample from 5 degrees to 20 degrees, or more particularly from 10degrees to 15 degrees.

As shown in FIG. 7, a sensor assembly 300 is similar to sensor assembly100. A piezoelectric material layer 314, similar to piezoelectricmaterial layer 114, is operatively connected directly to frame 302 todamp vibrations. Those skilled in the art will readily appreciate thatsuspended mass 304 can include a variety of electrical, optical and/ormechanical sensor components, and/or accessories therefor. It iscontemplated that piezoelectric material layer 314 can be a macro-fibercomposite (MFC) piezoelectric material layer, such as those describedabove.

Now with reference to FIG. 8, frame 302 includes inwardly extendingsupports 308 to which suspended mass 304 is suspended from, and a pairof endplates 310 spaced apart from one another along sensor axis A,similar to frame 102, described above. A pair of axially extending sidebeams 312 connects endplates 310. Piezoelectric material layers 314 arearranged similarly to piezoelectric material layers 114, except they aredirectly connected to frame 302, instead of through spacers.Piezoelectric material layers 314 are also operatively connected tosupports 308 of frame 302. It is also contemplated that piezoelectricmaterial layers 314 can be connected to side beams 312. In accordancewith some embodiments, a sensor assembly, e.g. sensor assembly 100, 200and/or 300, can include a variety of piezoelectric configurations. Forexample, some attached to a frame with spacers, some directly attachedto the frame and some layered within composite layers of the frame, aswill be described below. By applying the piezoelectric material layers314 directly to frame 302 or within the architecture of a frame, asdescribed below, the possibility that piezoelectric material layers,e.g. layer 314, will be damaged or knocked off during maintenance orrepair operations can be eliminated or reduced, increasing thedurability of the assembly over its service life.

As shown in FIGS. 9-11, a sensor assembly 400 is similar to sensorassembly 300. A piezoelectric material layer 414, similar topiezoelectric material layer 314, is operatively connected directly toframe 402 to damp vibrations. Frame 402 is made from at least one layerof fiber reinforced polymer (FRP) composite 403. Piezoelectric materiallayer 414 is layered, e.g. laminated, within FRP composite layers 403 ofrespective endplates 410 of frame 402. Layers 403 are visible in thecross-sectional view of FIG. 11 in supports 408. Similar FRP compositelayers 403 make up endplates 410. It is contemplated that frame 402 caninclude any suitable number of FRP composite layers 403. Piezoelectricmaterial layer 414 can be a macro-fiber composite (MFC) piezoelectricmaterial layer, as described above. Frame 402 includes inwardlyextending supports 408 to which suspended mass 404 is suspended from.Supports 408 also include layers of FRP composite material 403. Inaccordance with one embodiment, piezoelectric material layers 414 arelayered within FRP composite layers 403 of respective supports 408 offrame 402. Frame 402 includes a pair of axially extending side beams 412connecting endplates 410. It is also contemplated that piezoelectricmaterial layers 414 can be laminated within side beams 412.

While frames, e.g. frames 102, 202, 302 and 402, are shown as singleframes, it is contemplated that, in some embodiments, the frames areintermediate frames between their respective suspended masses andrespective outer frames. An outer frame is similar to the intermediateframe, e.g. frames 102, 202, 302 and 402, in that it can include apiezoelectric material layer, e.g. piezoelectric material layers 114,214, 314, and/or 414, applied directly thereon, through a spacer, and/orthrough lamination in the frame itself. The outer frame similarlyincludes a suspended mass within its interior. The piezoelectricmaterial layer, described above, is operatively connected to the outerframe to damp vibrations of the suspended mass. For the outer frame,however, there is one or more intermediate frames between the suspendedmass (or masses) and the outer frame. The outer frame can includesupports, e.g. supports 108, 208, 308 and/or 408, to connect it to theintermediate frame. The intermediate frame, in turn, operativelyconnects the suspended mass to the outer frame.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for sensor assemblies with superiorproperties including enhanced sensor imaging and/or data collectingcapabilities due to reduced vibration and reduced weight. While theapparatus and methods of the subject disclosure have been shown anddescribed with reference to preferred embodiments, those skilled in theart will readily appreciate that changes and/or modifications may bemade thereto without departing from the spirit and scope of the subjectdisclosure.

What is claimed is:
 1. A sensor assembly comprising: a frame; asuspended mass within an interior of the frame defining a sensor axis;and a piezoelectric material layer operatively connected to the frame todamp vibrations of the suspended mass.
 2. A sensor assembly as recitedin claim 1, wherein the frame includes fiber reinforced polymer (FRP)composite layers, wherein the piezoelectric material layer is layeredbetween the composite layers.
 3. A sensor assembly as recited in claim1, wherein the piezoelectric material layer is a macro-fiber composite(MFC) piezoelectric material layer.
 4. A sensor assembly as recited inclaim 1, wherein the frame includes inwardly extending supports to whichthe suspended mass is suspended from.
 5. A sensor assembly as recited inclaim 4, wherein the piezoelectric material layer is operativelyconnected to one of the supports of the frame.
 6. A sensor assembly asrecited in claim 4, wherein at least one of the supports includes FRPcomposite layers, wherein the piezoelectric material layer is layeredbetween the FRP composite layers of at least one of the supports of theframe.
 7. A sensor assembly as recited in claim 1, wherein the frameincludes a pair of endplates spaced apart from one another along thesensor axis, and a pair of axially extending side beams connecting thepair of endplates.
 8. A sensor assembly as recited in claim 7, whereinthe piezoelectric material layer is operatively connected to an outersurface of one of the endplates of the frame.
 9. A sensor assembly asrecited in claim 7, wherein the piezoelectric material layer isoperatively connected to an inner surface of one of the endplates of theframe.
 10. A sensor assembly as recited in claim 7, wherein at least oneof the endplates of the frame includes FRP composite layers, wherein thepiezoelectric material layer is layered between the FRP composite layersof at least one of the endplates.
 11. A sensor assembly comprising: aframe defining a sensor axis having opposing endplates with axiallyextending supports, wherein the opposing endplates are connected by apair of axially extending side beams; a suspended mass suspended withinan interior of the frame from the supports of the frame; and a pluralityof piezoelectric material layers operatively connected to the endplatesand supports of the frame to damp vibrations of the suspended mass. 12.A sensor assembly as recited in claim 11, wherein the piezoelectricmaterial layer is a macro-fiber composite (MFC) piezoelectric materiallayer.
 13. A sensor assembly as recited in claim 11, wherein the frameincludes FRP composite layers, and wherein at least one of thepiezoelectric material layers is layered between the FRP compositelayers of the frame.
 14. A sensor assembly as recited in claim 11,wherein the piezoelectric material layer is operatively connected to oneof the supports of the frame.
 15. A sensor assembly as recited in claim11, wherein the piezoelectric material layer is operatively connected toone of the endplates of the frame.